1. Field of the Invention
The present invention relates in general to transfer switches configured for use with portable power generation devices, for powering traffic signals and the like, during periods of unavailability of utility line power.
2. Background Art
When the utility line power to an electrically powered and controlled traffic signal fails, it is imperative to arrange for an alternative power supply as quickly as possible, so that the traffic signal can resume operation. Otherwise, police officers typically must man the intersection where the non-functioning traffic signal is located, or else the motoring and pedestrian public is placed in danger from traffic through an uncontrolled intersection. Using police officers or other personnel not only is an inefficient use of manpower, but also can be dangerous to the individuals manning the intersection, as they typically must position themselves in the midst of traffic in order to be seen, to provide traffic control guidance.
Usually, the method of supplying auxiliary power comprises the placement of a small portable generator, usually powered by a gasoline internal combustion engine, next to the traffic signal control pedestal, and electrically connecting the power output connections of the generator to the power input connections of the traffic signal control pedestal.
However, simply breaking the hardwire connection between the traffic signal controller and the utility line, and making a hardwire connection directly between the generator output and the traffic signal controller input, is a time consuming, inefficient and inelegant solution. One cannot splice in the generator input without disconnecting the utility line, as that could result in the accidental driving of current back up the utility line, which could, in turn, result in utility equipment damage as well as grave personal injury.
Accordingly, it is known to connect a power transfer switch to the traffic signal controller, the line utility and to a portable generator output, so that the traffic signal controller may be safely switched back and forth between the line utility and the generator. In areas where the utility power may be interrupted not infrequently (such as in areas where weather is often severe), having a transfer switch more or less permanently mounted onto a traffic signal controller makes supplying power as simple as bringing a generator to the traffic signal controller.
Uischner et al., U.S. Pat. No. 6,094,130 discloses an emergency power station for traffic signals, in which a fuel supply, a self-starting generator, and an automatic transfer switch, which is connected to the general utility power supply of the traffic signal. The automatic transfer switch is configured to sense when the utility power fails. After a predetermined delay, the generator engine is started, to provide power to the signal. The unit is provided with red and green signal lights which indicate which power source (generator and utility, respectively) is being used at the moment. However, such a complete self-contained system would be both expensive to manufacture, and typically more equipment than is typically required, even if such an apparatus were to be actually commercially available.
Flegel, U.S. Pat. No. 6,121,897 discloses a transfer switch to be mounted onto an existing traffic signal control pedestal, and connected to a portable electrical power generator. A gasket seal is provided in the hinged front door to the housing, to prevent ingress of moisture, dirt, etc.; however, this gasket appears to extend around only the sides and top of the interior of the side-hinged cover, leaving a clear gap at the bottom of the cover-housing interface. The transfer switch uses a three-position rotary switch, to flip between “line” (connecting the utility to the signal controller), “off” (both circuits disconnected), and “generator” (connecting the generator to the signal controller). While this manual transfer switch construction is considerably simpler than the fully automated station of the Uischner et al., U.S. Pat. No. 6,094,130 station, it lacks protection for the circuits.
It would be desirable to provide a simplified, basic transfer switch apparatus, for use with a traffic signal controller, which is provided with provisions for protection of the circuits.
It would also be desirable to provide a transfer switch apparatus for use with a traffic signal controller, which is provided with an indicator, to show when power to a utility line has been restored, so that upon remote visual inspection of the apparatus, one can see that it is possible to shut off a generator, and restore connection to utility power.
These and other desirable characteristics of the present invention will become apparent in view of the present specification, including claims, and drawings.